Telescopic blade PDC (Polycrystalline Diamond Compact) drill bit

Abstract

The invention belongs to the technical field of drilling equipment, and particularly relates to a PDC drill bit with telescopic blades. The telescopic blade PDC drill bit comprises an outer cylinder; the at least one fixed blade is fixedly arranged at the end part of the outer cylinder; the at least one movable blade is arranged at the end part of the outer cylinder in a sliding manner along the axial direction; the telescopic mechanism is arranged in the outer barrel, the telescopic mechanism is connected with the movable cutter wing, and the telescopic mechanism is arranged to respond to the pressure of drilling fluid and control the movable cutter wing to stretch out and draw back in the axial direction, so that the movable cutter wing is in a working state or a non-working state. The number of the blades can be changed so as to adapt to stratums with large lithology changes.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling equipment, and in particular relates to a telescopic blade PDC drill bit. Background Art

[0002] The drill bit is the main component of drilling equipment. Its main function is to break rocks and form wellbores. It is used in the oil and gas, geological exploration and drilling industries.

[0003] PDC drill bits are tools that use polycrystalline diamond composite sheets as cutting elements to break rocks by scraping. The blades of conventional PDC drill bits are fixed, and the number of blades on the drill bit is determined according to the formation conditions. In other words, different formations often require drill bits with different blade numbers and structures to maximize drilling efficiency. PDC drill bits suitable for hard and difficult-to-drill formations have a large number of blades, which can be arranged with more cutting teeth, which can increase the service life of the drill bit in hard and difficult-to-drill formations, but will reduce the ability of the drill bit to penetrate the formation; PDC drill bits suitable for medium-soft formations can increase the ability of the drill bit to penetrate the formation by reducing the tooth density, and have high rock breaking efficiency, but their service life will be negatively affected. When encountering formations with large lithology changes during drilling, a single drill bit blade number and cutting structure cannot match multiple formations at the same time. At this time, neither the drill bit life nor the drill bit rock breaking efficiency can be guaranteed, and the drill bit needs to be frequently pulled out of the hole to replace the drill bit, which undoubtedly prolongs the drilling cycle and increases drilling costs. Therefore, it is difficult for traditional PDC drill bits to simultaneously improve the drill bit's mechanical penetration rate and drill bit life in heterogeneous formations, and they have poor adaptability to formations with large lithology changes. Summary of the invention

[0004] In view of the technical problems mentioned above, the present invention aims to provide a telescopic blade PDC drill bit, which can change the number of blades to adapt to strata with large lithology variations.

[0005] According to the present invention, there is provided a telescopic blade PDC drill bit, comprising:

[0006] outer cylinder;

[0007] At least one fixed blade wing fixedly arranged at the end of the outer cylinder;

[0008] At least one movable blade wing is axially slidably arranged at the end of the outer cylinder;

[0009] And a telescopic mechanism is arranged in the outer tube, the telescopic mechanism is connected to the movable blade, and the telescopic mechanism is arranged to respond to the pressure of the drilling fluid to control the movable blade to extend and retract along the axial direction, so that the movable blade is in a working state or a non-working state.

[0010] In a specific embodiment, the telescopic mechanism includes a core tube coaxially slidably arranged in the outer tube, and one end of the core tube is fixedly connected to the movable blade wing.

[0011] In a specific embodiment, the telescopic mechanism further comprises:

[0012] An elastic member, wherein two axial ends of the elastic member are respectively connected to the core tube and the outer tube;

[0013] A slip ring shaft, the slip ring shaft is rotatably arranged in the outer cylinder along the circumferential direction;

[0014] A sheave assembly, wherein the sheave assembly is coaxially fixed on the core tube, and the sheave assembly is adapted to the slip ring shaft.

[0015] A differential pressure surface for responding to drilling fluid pressure is provided at the end of the core tube.

[0016] In a specific embodiment, the sheave assembly includes an upper sheave and a lower sheave that are coaxially fixedly connected, a plurality of first slopes are evenly arranged along the circumference at the lower end of the upper sheave, a plurality of second slopes are evenly arranged along the circumference at the upper end of the lower sheave, a low-level groove and a high-level groove are respectively arranged at both ends of the second slope, and the low-level groove and the high-level groove correspond to two adjacent first slopes, respectively.

[0017] In a specific embodiment, a sliding ring is coaxially rotatably arranged on the inner wall of the outer cylinder, at least one sliding ring shaft is arranged on the inner wall of the sliding ring, and the central axis of the sliding ring shaft coincides with the diameter of the sliding ring.

[0018] In a specific embodiment, the slip ring shaft is rotatably connected to the slip ring via a bearing.

[0019] In a specific embodiment, when the movable blade wing is in a working state, the height difference between the working end surfaces of the movable blade wing and the fixed blade wing is zero, and when the movable blade wing is in a non-working state, the height difference between the working end surfaces of the movable blade wing and the fixed blade wing is 0 to 5 mm.

[0020] In a specific embodiment, the movable blade wing is fixedly connected to the core tube via a pin shaft, a pin hole is radially arranged on the outer wall of the core tube, a through hole is radially arranged on the movable blade wing, and the pin shaft is arranged in the pin hole and the through hole.

[0021] In a specific embodiment, the outer cylinder comprises:

[0022] outer shell;

[0023] An upper joint disposed at the upper end of the outer shell;

[0024] and a lower joint disposed at the lower end of the outer shell;

[0025] Wherein, the two axial ends of the elastic member abut against the core tube and the lower joint respectively, and the slip ring shaft is arranged between the upper joint and the outer shell.

[0026] In a specific embodiment, a drill body is fixedly disposed at one end of the lower joint away from the outer shell, the fixed blade is fixedly disposed on the drill body, and the movable blade is axially sealed and slidably disposed on the drill body.

[0027] Compared with the prior art, the advantages of the present application are as follows.

[0028] The present invention is provided with a fixed blade, a movable blade and a telescopic mechanism. The telescopic mechanism can respond to the pressure of the drilling fluid and drive the movable blade to extend and retract axially, so as to adjust the number of blades of the drill bit downhole according to the change of the formation encountered by drilling, thereby overcoming the disadvantage of poor formation adaptability of the existing fixed blade drill bit, and having stronger adaptability to the well section with repeated changes in formation properties. When facing hard formations, the telescopic mechanism responds to the pressure of the drilling fluid and causes the movable blade to extend axially outward. At this time, the movable blade and the fixed blade work together for drilling. The number of blades is large, and more cutting teeth can be arranged, which can improve the service life of the drill bit in hard and difficult-to-drill formations; when facing medium-soft formations, the telescopic mechanism responds to the pressure of the drilling fluid and causes the movable blade to retract axially inward. At this time, only the fixed blade is used for drilling. The number of blades is small, which can improve the ability of the drill bit to penetrate the formation and improve the rock breaking efficiency.

[0029] The relative height difference between the fixed blade and the movable blade can be changed according to the designed groove wheel assembly parameters, thereby extending the service life of the drill bit while ensuring the rock breaking efficiency of the drill bit. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be described below with reference to the accompanying drawings.

[0031] Figure 1 A schematic diagram showing the appearance structure of a telescopic blade PDC drill bit according to an embodiment of the present invention is shown;

[0032] Figure 2 A cross-sectional view showing an embodiment of a telescopic blade PDC drill bit according to the present invention;

[0033] Figure 3 shows a schematic diagram of a core tube according to the present invention;

[0034] Figure 4 A schematic diagram of a sheave assembly according to the present invention is shown;

[0035] Figure 5shows a schematic diagram of a slip ring according to the present invention;

[0036] Figure 6 Shows an expanded schematic diagram of a sheave assembly according to the present invention;

[0037] Figure 7 to Figure 11 It is a schematic diagram of different positions of the sheave assembly and the slip ring shaft working together;

[0038] Fig.12 A schematic diagram of a movable blade according to the present invention is shown.

[0039] In the figure: 20, outer cylinder; 30, telescopic mechanism; 1, upper joint; 2, sliding ring; 3, bearing; 4, sliding ring shaft; 5, outer shell; 6, elastic member; 7, lower joint; 8, pin shaft; 9, groove wheel assembly; 91, upper groove wheel; 92, lower groove wheel; 910, first slope; 920, second slope; 921, low position groove; 922, high position groove; 10, cutting tooth; 11, movable blade; 12, nozzle; 13, fixed blade; 14, core tube; 140, pin hole; 141, pressure difference surface; 142, small diameter part; 143, large diameter part; 15, liquid flow channel; 110, drill bit body; 111, through hole; 1101, center axis; 100, telescopic blade PDC drill bit.

[0040] In the present application, all drawings are schematic drawings, which are only used to illustrate the principles of the present invention and are not drawn according to the actual scale. DETAILED DESCRIPTION

[0041] The present invention will be described below with reference to the accompanying drawings.

[0042] It should be noted that, in the present application, the direction in which the fixed blade wing 13 is provided according to the present invention is described as "downward" or similar terms, that is, Figure 1 and the end provided with the upper connector 1 is described as "upper" or similar terms, that is, Figure 1 on the left side.

[0043] Figure 1 The structure of the telescopic blade PDC drill bit 100 according to the present invention is shown. Figure 1 and Figure 2 As shown, the telescopic blade PDC drill bit 100 includes an outer cylinder 20 , a fixed blade 13 , a movable blade 11 and a telescopic mechanism 30 .

[0044] At least one fixed blade wing 13 is fixedly provided at the lower end of the outer cylinder 20 , and at least one movable blade wing 11 is slidably provided.

[0045] The telescopic mechanism 30 is arranged inside the outer cylinder 20. Specifically, a liquid flow channel 15 for the drilling fluid to flow through is arranged inside the outer cylinder 20. The telescopic mechanism 30 is arranged in the liquid flow channel 15 inside the outer cylinder 20. The lower end of the telescopic mechanism 30 is connected to the movable blade 11. The telescopic mechanism 30 is arranged to respond to the pressure of the drilling fluid and control the movable blade 11 to extend and retract along the axial direction, so that the movable blade 11 is in a working state or a non-working state.

[0046] In a specific embodiment, the outer cylinder 20 includes an upper joint 1, an outer shell 5, a lower joint 7 and a drill bit body 110 which are coaxially fixedly connected in sequence from top to bottom.

[0047] The upper end of the upper joint 1 is provided with an external thread for connecting with other downhole tools. The lower end of the upper joint 1 is provided with an internal thread, and the upper end of the outer shell 5 is provided with an internal thread, and the upper joint 1 and the outer shell 5 are fixedly connected by threads. The lower end of the outer shell 5 is provided with an internal thread, and the upper end of the lower joint 7 is provided with an external thread, and the outer shell 5 and the lower joint 7 are fixedly connected by threads. The drill bit body 110 is fixedly provided at the lower end of the lower joint 7.

[0048] A nozzle 12 connected to the fluid flow channel 15 is disposed at the lower end of the drill bit body 110 . The drilling fluid can flow to the outside of the telescopic blade PDC drill bit 100 through the fluid flow channel 15 and the nozzle 12 .

[0049] A plurality of fixed blades 13 are evenly arranged at the lower end of the drill body 110 along the circumferential direction, and a plurality of cutting teeth 10 are arranged on the fixed blades 13. A plurality of movable blades 11 are evenly arranged on the drill body 110 along the circumferential direction, and a plurality of cutting teeth 10 are arranged on the movable blades 11. Each movable blade wing 11 is arranged on the drill body 110 along the direction of the central axis by a sealed sliding connection, and the movable blade wing 11 is fixedly connected to the telescopic mechanism 30. The tooth profiles of the fixed blades 13 and the movable blades 11 and the cutting teeth 10 arranged thereon can be designed with reference to the blades in the prior art.

[0050] In a preferred embodiment, the cutting teeth 10 arranged on the movable blade wing 11 and the fixed blade wing 13 are one or a combination of PDC teeth, rotary cutting teeth, buffer teeth, gear teeth, etc., which can cope with different formation conditions.

[0051] In a preferred embodiment, baffles (not shown in the figure) for restricting the circumferential deformation of the movable blades 11 are provided on the drill body 110 , and the number of the baffles is the same as the number of the movable blades 11 .

[0052] In the present invention, if Figure 1 to Figure 3 as well as Fig.12As shown, the telescopic mechanism 30 includes a core tube 14 coaxially slidably arranged in the outer tube 20, and the lower end of the core tube 14 is fixedly connected to the movable blade wing 11. At least one through hole 111 is radially arranged on the movable blade wing 11, and a pin hole 140 corresponding to the through hole 111 is arranged on the core tube 14. When the movable blade wing 11 and the core tube 14 are fixed to each other, the lower end surface of the movable blade wing 11 and the core tube 14 are axially abutted, and the axis of the through hole 111 of the movable blade wing 11 coincides with the axis of the pin hole 140 of the core tube 14, and the pin shaft 8 enters inward from the outer side of the movable blade wing 11 along the through hole 111, and finally enters the pin hole 140 of the core tube 14, and part of the length of the pin shaft 8 is located in the pin hole 140, and the other part of the length of the pin shaft 8 is located in the through hole 111.

[0053] In order to enhance the connection strength between the core tube 14 and the movable blade wing 11 , a plurality of pin holes 140 and through holes 111 may be provided.

[0054] Specifically, the core tube 14 includes a coaxially fixedly connected large diameter portion 143 and a small diameter portion 142. The inner diameters of the small diameter portion 142 and the large diameter portion 143 are equal, and the outer diameter of the large diameter portion 143 is greater than the outer diameter of the small diameter portion 142.

[0055] The upper end of the lower joint 7 extends to the inside of the outer shell 5, that is, the inner diameter of the upper end of the lower joint 7 is smaller than the inner diameter of the lower end of the outer shell 5. The outer wall of the large diameter portion 143 contacts the inner wall of the outer shell 5, and the outer wall of the small diameter portion 142 contacts the inner wall of the lower joint 7.

[0056] An annular space is formed between the large diameter portion 143, the small diameter portion 142, the lower joint 7 and the outer shell 5, and an elastic member 6 is arranged in the annular space. Specifically, the elastic member 6 is coaxially sleeved on the small diameter portion 142, and the axial ends of the elastic member 6 abut against the large diameter portion 143 and the lower joint 7 respectively.

[0057] In a specific embodiment, the elastic member 6 can be any one of a spring, a disc spring, and rubber.

[0058] When the movable blade 11 is in a non-working state, under the action of the force of the elastic member 6, the upper end of the core tube 14 axially abuts against the upper joint 1, and at the same time, the upper end of the movable blade 11 axially abuts against the lower joint 7, that is, Figure 2 Preferably, at this time, the height difference between the working end faces of the movable blade wing 11 and the fixed blade wing 13 is 0-5mm, that is, the lowermost end of the movable blade wing 11 is higher than the lowermost end of the fixed blade wing 13, and the height difference between the lowermost end of the movable blade wing 11 and the lowermost end of the fixed blade wing 13 is greater than zero and less than 5mm. At this time, only the fixed blade wing 13 participates in the rock breaking work and performs drilling.

[0059] When the movable blade wing 11 is in working state, the height difference between the working end surfaces of the movable blade wing 11 and the fixed blade wing 13 is zero. At this time, the movable blade wing 11 and the fixed blade wing 13 drill the formation together.

[0060] According to the present invention, Figure 2 As shown, a slip ring shaft 4 is coaxially rotatably arranged on the inner wall of the outer cylinder 20, and a sheave assembly 9 is coaxially fixedly arranged on the core tube 14, and the sheave assembly 9 is adapted to the slip ring shaft 4. The sheave assembly 9 can be fixedly connected to the core tube 14 by an integral molding method; or a setting method in which they are processed separately and then fixedly connected is adopted.

[0061] Specifically, Figure 4 As shown, the sheave assembly 9 includes an upper sheave 91 and a lower sheave 92 that are coaxially fixedly connected. A plurality of first slopes 910 are evenly arranged along the circumference at the lower end of the upper sheave 91, and a plurality of second slopes 920 are evenly arranged along the circumference at the upper end of the lower sheave 92. The first slopes 910 and the second slopes 920 have opposite inclination directions. A space for accommodating the slip ring shaft 4 is reserved between the first slopes 910 and the second slopes 920. The motion trajectory of the slip ring shaft 4 between the first slopes 910 and the second slopes 920 is shown in FIG. Figure 7 to Figure 11 As shown, it is described in detail below.

[0062] like Figure 4 and Figure 6 As shown, low slots 921 and high slots 922 are respectively arranged at both ends of each second slope 920, that is, the low slots 921 and high slots 922 are alternately arranged in sequence. At the same time, the low slots 921 and high slots 922 correspond to the inclined surfaces of two adjacent first slopes 910, respectively.

[0063] Combination Figure 2 as well as Figure 7 to Figure 11 The working principle of the groove wheel assembly 9 and the slip ring shaft 4 is as follows.

[0064] Figure 2 The core tube 14 and the movable blade 11 are in a retracted state, that is, the movable blade 11 is in a non-working state. At this time, the positional relationship between the groove wheel assembly 9 and the slip ring shaft 4 is as follows: Figure 7 As shown, the slip ring shaft 4 is located in the low position groove 921 .

[0065] When the movable blade 11 needs to be extended, that is, the movable blade 11 and the fixed blade 13 work together, the pressure of the drilling fluid in the flow channel 15 is increased, and the core tube 14 moves downward relative to the outer tube 20 in response to the pressure of the drilling fluid, compressing the elastic member 6. Since the core tube 14 is fixedly connected to the groove wheel assembly 9, the slip ring shaft 4 is axially fixed and axially rotated relative to the outer tube 20, so at this time the groove wheel assembly 9 moves along the groove wheel assembly 9. Figure 7The arrow direction in FIG. 1 moves downward relative to the slip ring shaft 4 until the slip ring shaft 4 abuts against the first slope 910, as shown in FIG. Figure 8 shown.

[0066] The sheave assembly 9 continues to move downward, and the slip ring shaft 4 rotates in the circumferential direction under the action of the inclined surface of the first slope 910, that is, the slip ring shaft 4 rotates in the circumferential direction. Fig. 9 until the slip ring shaft 4 moves between two adjacent first slopes 910, as shown in FIG. Fig. 9 shown.

[0067] Then, the drilling fluid pressure in the flow channel 15 is reduced, and the core tube 14 begins to return upward under the action of the elastic member 6. At the same time, the sheave assembly 9 also moves upward. Fig.10 As shown, the sheave assembly 9 moves upward relative to the slip ring shaft 4 along the direction of the arrow in the figure until the slip ring shaft 4 contacts the second ramp 920 .

[0068] The groove wheel assembly 9 moves upward, and the slip ring shaft 4 rotates in the circumferential direction under the action of the inclined surface of the second slope 920, that is, the slip ring shaft 4 moves in the circumferential direction. Fig.11 Move on the right side, until the slip ring shaft 4 moves to the high-level groove 922. So far, the core tube 14 drives the movable blade wing 11 to move downwards to be flush with the fixed blade wing 13, and the movable blade wing 11 is fixed.

[0069] When the movable blade 11 needs to be retracted, that is, only the fixed blade 13 needs to work, the drilling fluid pressure in the liquid flow channel 15 is increased and decreased again in sequence, and the above-mentioned operation process is repeated to make the slip ring shaft 4 located in the low-position groove 921.

[0070] Repeat the above process. Since the groove wheel assembly 9 is connected to the core tube 14, and the core tube 14 is connected to the movable blade wing 11, the change of the position of the core tube 14 and the groove wheel assembly 9 can realize the free switching of the extended and retracted states of the movable blade wing 11.

[0071] By setting the height difference between the high-position groove 922 and the low-position groove 921 , the height difference between the movable blade wing 11 and the fixed blade wing 13 in the non-working state can be controlled.

[0072] In a preferred embodiment, in order to allow the movable blade wing 11 to have different extension amounts so as to achieve different relative working heights for the movable blade wing 11 and the fixed blade wing 13, the lower groove wheel 92 can be configured to have multiple groups of different extreme positions (high grooves 922 and low grooves 921 with different height differences are configured), preferably 1 to 3 groups.

[0073] In a specific embodiment, in order to enable the core tube 14 to respond to the pressure of the drilling fluid, such as Figure 2As shown, a pressure differential surface 141 for responding to drilling fluid pressure is provided at the upper end of the core tube 14. The pressure-bearing area of ​​the upper end of the core tube 14 is larger than the pressure-bearing area of ​​the lower end. Therefore, when the core tube 14 is in a pressure environment, the pressure difference between the upper and lower ends of the core tube 14 is larger than the elastic force of the elastic member 6, and the core tube 14 can overcome the force of the elastic member 6 and move downward.

[0074] In a preferred embodiment, Figure 2 and Figure 5 As shown, a slip ring 2 is coaxially rotatably arranged on the inner wall of the outer cylinder 20, at least one slip ring shaft 4 is arranged on the inner wall of the slip ring 2, and the central axis of the slip ring shaft 4 coincides with the diameter of the slip ring 2. In this embodiment, three slip ring shafts 4 are evenly arranged on the inner wall of the slip ring 2 along the circumferential direction, so that the slip ring shaft 4 and the groove wheel assembly 9 are more stable when adapted.

[0075] The slip ring shaft 4 and the slip ring 2 may be integrally formed, or the slip ring shaft 4 and the slip ring 2 may be connected by welding or interference fit.

[0076] It is easy to understand that, although three slip ring shafts 4 are provided in this embodiment, the present invention is not limited to providing three slip ring shafts 4, and those skilled in the art can change the number of slip ring shafts 4 according to the present invention and in combination with actual conditions. It is easy to understand that the number of the first slope 910 and the second slope 920 of the sheave assembly 9 also changes according to the number of slip ring shafts 4. Such changes should be within the scope of protection of the present invention.

[0077] In a preferred embodiment, Figure 2 As shown, the slip ring shaft 4 is rotatably connected to the slip ring 2 via the bearing 3. The rotation axis of the slip ring shaft 4 coincides with the diameter of the slip ring 2. Under this arrangement, when the slip ring shaft 4 moves along the first slope 910 and the second slope 920, the friction between them can be reduced.

[0078] In a preferred embodiment, the slip ring shaft 4 and the slip ring 2 are arranged between the connection gap between the upper joint 1 and the outer shell 5. Specifically, in this embodiment, Figure 2 As shown, the upper end of the sliding ring 2 contacts the upper joint 1, the lower end of the sliding ring 2 contacts the outer shell 5, and the outer wall of the sliding ring 2 contacts the upper joint 1. This arrangement can facilitate the installation and removal of the sliding ring 2.

[0079] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0080] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0081] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0082] Finally, it should be noted that the above is only a preferred embodiment of the present invention and does not constitute any limitation to the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the aforementioned embodiments or to replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A telescopic blade PDC drill bit, characterized in that: include: outer cylinder(20); At least one fixed blade (13) fixedly arranged at the end of the outer cylinder (20); At least one movable blade (11) slidably arranged at the end of the outer cylinder (20) in the axial direction; and a telescopic mechanism (30) disposed in the outer cylinder (20), the telescopic mechanism (30) being connected to the movable blade (11), the telescopic mechanism (30) being configured to respond to the pressure of the drilling fluid and control the movable blade (11) to telescope in the axial direction, thereby placing the movable blade (11) in a working state or a non-working state.

2. The telescopic blade PDC drill bit according to claim 1, characterized in that: The telescopic mechanism (30) comprises a core tube (14) coaxially slidably arranged in the outer tube (20), and one end of the core tube (14) is fixedly connected to the movable blade (11).

3. The telescopic blade PDC drill bit according to claim 2, characterized in that: The telescopic mechanism (30) further comprises: An elastic member (6), wherein two axial ends of the elastic member (6) are respectively connected to the core tube (14) and the outer tube (20); A slip ring shaft (4), the slip ring shaft (4) being rotatably arranged in the outer cylinder (20) along the circumferential direction; A sheave assembly (9), wherein the sheave assembly (9) is coaxially fixed on the core tube (14), and the sheave assembly (9) is adapted to the slip ring shaft (4). A pressure difference surface (141) for responding to drilling fluid pressure is provided at the end of the core tube (14).

4. The telescopic blade PDC drill bit according to claim 3, characterized in that: The sheave assembly (9) comprises an upper sheave (91) and a lower sheave (92) which are coaxially fixedly connected, a plurality of first slopes (910) are evenly arranged along the circumference at the lower end of the upper sheave (91), a plurality of second slopes (920) are evenly arranged along the circumference at the upper end of the lower sheave (92), a low-level groove (921) and a high-level groove (922) are respectively arranged at both ends of the second slope (920), and the low-level groove (921) and the high-level groove (922) respectively correspond to two adjacent first slopes (910).

5. The telescopic blade PDC drill bit according to claim 3, characterized in that: A sliding ring (2) is coaxially rotatably arranged on the inner wall of the outer cylinder (20), at least one sliding ring shaft (4) is arranged on the inner wall of the sliding ring (2), and the central axis of the sliding ring shaft (4) coincides with the diameter of the sliding ring (2).

6. The telescopic blade PDC drill bit according to claim 5, characterized in that: The slip ring shaft (4) is rotatably connected to the slip ring (2) via a bearing (3).

7. The telescopic blade PDC drill bit according to any one of claims 1 to 6, characterized in that: When the movable blade wing (11) is in a working state, the height difference between the working end surfaces of the movable blade wing (11) and the fixed blade wing (13) is zero; when the movable blade wing (11) is in a non-working state, the height difference between the working end surfaces of the movable blade wing (11) and the fixed blade wing (13) is 0 to 5 mm.

8. The telescopic blade PDC drill bit according to any one of claims 2 to 6, characterized in that: The movable blade (11) is fixedly connected to the core tube (14) via a pin shaft (8); a pin hole (140) is radially arranged on the outer wall of the core tube (14); a through hole (111) is radially arranged on the movable blade (11); and the pin shaft (8) is arranged in the pin hole (140) and the through hole (111).

9. The telescopic blade PDC drill bit according to any one of claims 3 to 6, characterized in that: The outer cylinder (20) comprises: An outer shell (5); An upper joint (1) arranged at the upper end of the outer shell (5); and a lower joint (7) arranged at the lower end of the outer shell (5); The two axial ends of the elastic member (6) respectively abut against the core tube (14) and the lower joint (7), and the slip ring shaft (4) is arranged between the upper joint (1) and the outer shell (5).

10. The telescopic blade PDC drill bit according to claim 9, characterized in that: A drill body (110) is fixedly arranged at one end of the lower joint (7) away from the outer shell (5), the fixed blade (13) is fixedly arranged on the drill body (110), and the movable blade (11) is axially sealed and slidably arranged on the drill body (110).

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